KLT is a sanitation services company specializing in small cleaning job and mold remediation. Each client pays a fixed monthly service fee based on the number of rooms in the building. Records are kept on the time and material costs used for each repair. The following profitability data apply to four customers: Customer Revenues Customer Costs D Ross $360 $270 S Miller 240 366 P Smythe 90 132 K Beukes 420 264 Who has the highest operating income among the four customers